This invention relates to an air intake system for a gas fueled engine and more particularly to an improved induction and charge forming system for an internal combustion engine and particularly one operating on a gaseous fuel.
In the interest of protecting the environment and conserving nature resources, it has been proposed to operate internal combustion engines on a gaseous fuel (L.P.G.). The gaseous fuel is stored under pressure as a liquid in a container and then is delivered to the engine through a regulating and induction system for its operation. In addition to the aforenoted environmental advantages, gaseous fuels tend to promote longer engine life and longer service intervals due to the fact that the burn more cleanly in the combustion chamber of the engine.
However, in order to assure the maximum advantages of gaseous fueled engines, it is desirable to insure that the induction system for the engine has optimum efficiency. For example, it is well known that it is desirable to induce turbulence in the combustion chamber, particularly at low speeds, in order to insure complete and rapid combustion. However, the induction of a turbulent charge into the combustion chamber reduces the volumetric efficiency of the engine and can reduce power outputs at high speeds.
It is, therefore, a principal object to this invention to provide an improved induction system for a gas fueled internal combustion engine that permits the generation of turbulence in the combustion chamber at low speeds without adversely effecting volumetric efficiency at high speeds.
In addition to the differences required for induction at low speed and high speed operations, there are a number of a various other running conditions of the engine which dictate differences in the performance of the induction system depending upon the actual speed and load of the engine. Devices which may operate to assist under one running condition, can be detrimental under another running condition. Therefore, induction systems employed with gas fueled engines have tended to be a compromise in order to operate satisfactorily, but less than most efficiently, under all conditions.
It is, therefore, a further object of this invention to provide an improved induction system and charge forming system for an internal combustion engine operated on a gaseous fuel wherein the induction system can be tailored to provide different charging effects under different running conditions.
As with other types of fuel on which internal combustion engines operate, it is necessary to mix the fuel with air so as to provide a stoichiometric mixture within the combustion chamber that can be easily ignited and which will burn efficiently and completely. It has generally been the practice to employ a charge former such as a carburetor for mixing the gaseous fuel with atmospheric air for delivery to the engine through its induction system. The gaseous fuel is supplied to the charge former from a source in which the fuel is stored under pressure as a liquid and a regulator is employed in the system between the source and the charge former. As with other forms of fuel, the charge former must provide good air and fuel mixing under all running conditions. This generally necessitates the formation of compound or plural discharge circuits in the carburetor. For example, it is conventional to employ an idle discharge circuit and a main fuel discharge circuit. Such carburetors are employed conventionally with gaseous fueled engines.
However, when operating with gaseous fuel there are some instances when it is not desirable to perform all of the fuel and air mixing within the charge former. That is, if all of the fuel/air mixing is accomplished within the charge former, the performance of the engine under running conditions such as idle or low speed operation or transient conditions may not be optimum.
It is, therefore, a still further object to this invention to provide an improved induction and charge forming system for a gaseous fueled engine wherein not all of the fuel is mixed with the air in the charge former.
It is a further object to this invention to provide an improved charge forming and induction system for a gaseous fueled engine wherein a major portion of the fuel/air mixing takes place in the charge former and other running conditions are accommodated by provided fuel at a supplemental location in the induction system.
One running condition that provides difficulty in insuring good fuel/air mixing and adequate fuel in the combustion chamber for combustion is during acceleration. Gaseous fuels like liquid fuels do not accelerate as rapidly as air flow when the engine is rapidly accelerated. This is due to the more dense nature of the fuel than the air. In order to reduce the likelihood of lean running, it is desirable to provide some additional fuel enrichment during the initial period when the throttle valve of the engine is rapidly opened.
These problems become even more acute when the acceleration takes place at the end of a long period of deceleration or at the end of a rapid deceleration. When the engine is being decelerated, the throttle valve is generally closed and little or no fuel is supplied. As a result, the area between the throttle valve and the combustion chamber will be depleted of fuel. Thus, when the throttle valve is rapidly opened, although the air flow may increase, it will take a long time for the fuel to reach the combustion chamber and poor running can occur.
It is, therefore, a still further object to this invention to provide an improved arrangement for supplying accelerating fuel to a gaseous fueled engine wherein lags in performance under acceleration are avoided.